Human granulocytic anaplasmosis (HGA, formerly HGE) is an emerging tick-borne infection caused by Anaplasma phagocytophilum, an obligate intracellular parasite of neutrophils. Patients develop a "flu-like" illness that can be severe with shock or respiratory distress. Death is infrequent, but abnormal host immunityand inflammation can lead to opportunistic infections. Infected neutrophils are simultaneously "activated" and "deactivated" resulting in a discoordinated proinflammatory response favoring infected cell accumulation and loss of microbicidal and regulatory capacity. Infected neutrophils have diminished transcription of some host genes for effector mechanisms and cell cycling. A. phagocytophilum AnkA protein is ferried from the parasitophorous vacuole to accumulate in the host cell nucleus, where it is the only known protein of the bacterium to enter the cell. Moreover, AnkA binds both host DNA and proteins, and binds particularly to matrix attachment regions that are known to significantly influence transcription of genes within 50 to 100 kb on the chromosome. Thus, we propose AnkA: 1. is rapidly transcribed and transported to the granulocyte nucleus; 2. mediates some of the neutrophil functional changes with A. phagocytophilum infection; 3. directly interacts with host cell chromatin to influence the transcription of host genes. We propose to i) describe the kinetics ofankA transcription and AnkA expression, and to examine whether other genes in proximity to ankA in the A.phagocytophilum genome are coordinately regulated; ii) characterize the effects of AnkA on neutrophil function; iii) demonstrate how A.phagocytophilum infection or AnkA affect transcription of key genes and neutrophil function by AnkA binding to specialized ATC chromatin structures, modificationofchromatin architecture and change in gene transcription at specific loci, with special emphasis on CYBB, RAC2, and IL8. Thus, we will evaluate how A.phagocytophilum and AnkA regulate gene transcription and consequently neutrophil function. The proposed model of control is not yet described for any bacterium and would provide a novel mechanism for bacterial control of infected hosts. These studies will provide a model for understanding how the bacterium lives in and subverts neutrophilsand should improve comprehension of disease pathogenesis. With this will come a strategy for design of prevention, management, and treatment of HGA, and a new model for investigatingthe neutrophil biology.